fix a couple more uses of def_kind

src/librustc_passes/dead.rs

@@ -558,7 +558,7 @@ fn warn_dead_code(
         if !name.as_str().starts_with('_') {
             self.tcx.struct_span_lint_hir(lint::builtin::DEAD_CODE, id, span, |lint| {
                 let def_id = self.tcx.hir().local_def_id(id);
-                let descr = self.tcx.def_kind(def_id).descr(def_id);
+                let descr = self.tcx.def_kind(def_id).descr(def_id.to_def_id());
                 lint.build(&format!("{} is never {}: `{}`", descr, participle, name)).emit()
             });
         }

src/librustc_passes/stability.rs

@@ -343,7 +343,7 @@ fn check_missing_stability(&self, hir_id: HirId, span: Span) {
             !self.tcx.sess.opts.test && stab.is_none() && self.access_levels.is_reachable(hir_id);
         if is_error {
             let def_id = self.tcx.hir().local_def_id(hir_id);
-            let descr = self.tcx.def_kind(def_id).descr(def_id);
+            let descr = self.tcx.def_kind(def_id).descr(def_id.to_def_id());
             self.tcx.sess.span_err(span, &format!("{} has missing stability attribute", descr));
         }
     }